Public API that does not require auth

It would be great if you don't need to authenticate for accessing some API properties for public projects.

This for instance for app devs: #4205 (closed)

Endpoints:

• API::Projects: !7843 (merged)
• API::Tags: !7896 (merged)
• API::Repositories: !8148 (merged)
• API::Files: !8149 (merged)